context: Provide global instance

This will avoid the increasingly ugly pushing around of a context
instance as parameter to various methods/functions. Everyone can now
simply call get_context() after build or shell called
create_global_context().

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas/shell.py

@@ -27,7 +27,7 @@
 import subprocess
 import os
 from .libkas import kasplugin
-from .context import Context
+from .context import create_global_context
 from .libcmds import (Macro, Command, SetupDir, SetupEnviron,
                       WriteBBConfig, SetupHome, ReposApplyPatches,
                       CleanupSSHAgent, SetupSSHAgent, SetupRepos)
@@ -75,7 +75,7 @@ class Shell:
         if args.cmd != 'shell':
             return False
 
-        ctx = Context(args.config, args.target, None)
+        ctx = create_global_context(args.config, args.target, None)
 
         macro = Macro()